Currently, there are over 80,000 chemicals in use and approximately 2000 new chemicals are introduced into use every year. Regulatory agencies have recognized the need for alternative toxicological methods and models to decrease the time and expense of current toxicity testing protocols. In association with the National Toxicology Program (NTP), our group is developing C. elegans as an alterative organism for in vivo toxicological testing. Short life cycles, easy and inexpensive maintenance and culturing, and detailed biological knowledge has allowed for the development of rapid, low-cost toxicity tests that readily lend themselves to mechanistic studies of toxicant actions. Because of the evolutionarily conserved nature of the stress-response and other relevant pathways, it is likely that responses elicited in C. elegans will be applicable to understanding similar processes in higher organisms, including humans.[unreadable] [unreadable] Our group has developed methods to measure the toxicity of known and suspected developmental and neurological toxicants. Protocols are regularly used to assess the effects of chemicals on the growth, size, reproduction, feeding, or movement of C. elegans. These technologies are based on a 96 well format, and required the adaptation of liquid handling robotics to C. elegans biology. The COPAS Biosort platform is similar to a fluorescence-activated cell sorter system and is used for dispensing and measuring C. elegans characteristics including length, optical density and fluorescence. Using this technology, our group is able to reliably quantify biological responses in a whole organism in a high throughput format.